I have had several duramax's all off which got 17-19 mpg most of the time. My father also has had several duramax's with similar results, and my grandfather (who babies his) gets 18-21.

Now in january my father and I both bought new 2008's..... holy smokes, both of us are lucky to get in the 13's, 12 most of the time.

I know we have a DPF now, but this is crazy. Anything I should look for? Both trucks have 5 to 6 thousand miles.

get rid of the dpf. i only had about 500 miles on my 08 when i got rid of all the factory emissions parts. i get 15.6 right now drivin around town all the time with whats in signature. it has about 2700 on it now and ive been told it will go up higher when the truck gets some more miles on it. we'll see what happens. take care

denny

My grandfather has a Cummins with the DPF and he does good to get 13. Stupid emissions crap.:mad:

The mileage claims are all over the board. I myself tried the baby it and was in the 13s myself. Finally said hell to it and drove like I stole it 60 percent of the time. and got up into the 15s. After 22,000 miles and no issues I said hell to it and dropped the DPF and went EFI Live with Nick from DuramaxTuner. I Average mid 17s now and still drive it like I stole and have done 21mpg at 75 for a couple hours on the interstate using a Tow tune from Nick but I am not towing with it. Just runs less boost and seems to help increase mileage.

Brian

D.....p.....f

I Got 2-3 Mpg Beytter Just By Removing It

The days of significantly better mileage w/ diesel over gassers in these LMM and future trucks is long gone unless you want to remove emissions equipment and spend some coin on a programmer and exhaust. glad I jumped in prior to 2007 EPA BS.

My 07 LMM had got better mileage then most the people here and I never touched the DPF. I drove it close to the speed limit and got there in a relaxed mannor.

The one I have now is a DRW and only has a few hundred miles so I cannot speak yet to it's mileage.

What is weird is my lmmgets better than my old lbz

What is weird is my lmmgets better than my old lbz
You are definitely in the minority there. I have talked to several people I know that sold 2006 LLY/LBZ's and are kicking themselves for moving into the LMM. I guess it worked out good for you.

Pound for pound, and assuming same load, terrain and speed, I would bet 9 out of 10 times the LMM get worse mileage than the LBZ's.

dont have a LMM but my LBZ never got the mileage that my LB7 or LLY got but, my LBZ would spank both of my older trucks like they were psycho nympho freaky ex-girlfriends!

My lbz might get 15- 15.5 mixed driving (city and highway) with ppe
My LMM gets 16.5 mixed with ppe at only 2500 miles it wll get even better... I dunno

all is hand calculated

Went down to look at some 08's. Salesman was the most honest guy you can find. Said the price of the new ones is up, your trade value is down and they get worse mileage too.

What is the DPF and EFI?

I am on my third tank of diesel and I am getting 20 mpg on the highway. I have had one regen and that dropped it a bit for about 10 minutes on the highway, then it went right back up after about 20 miles or so.

My truk is a 07 ltz x cab 4x4. I don't dirve it real hard and I don't baby it. I hope it gets better for you guys getting 12-13!!! Mark

What is the DPF and EFI?
dpf is diesel particulate filter

efi live is programming software. do a search on either this site or google

the exhaust you need to get rid of it. i was told about every 5,00 mile you need to take it to the dealer to get the exhaust cleanedor something like that from a buddy of mine that has a 08 lmm c/c drw and he deleted the exhaust and place magnaflow and got 19and 22 on highway then city about 17. and he opened the air intake system. i think he went to afe or airraid.

I am on my 3rd tank of diesel and I haven't gotten less than 16 mpg on my new LMM.

the exhaust you need to get rid of it. i was told about every 5,00 mile you need to take it to the dealer to get the exhaust cleanedor something like that from a buddy of mine that has a 08 lmm c/c drw and he deleted the exhaust and place magnaflow and got 19and 22 on highway then city about 17. and he opened the air intake system. i think he went to afe or airraid.
First off that wasn't english and second a complete lie.

First off that wasn't english and second a complete lie.


well just to clear it up for you i did call a local dealer and yes there is a such thing. its a diesel exhaust cleaning they do something to the back part of the exuast. so thanks you asked for help and i gave. if im lieing why dont you call your lacal dealer that has a diesel tech there, and tell them you pull a trailer, and the truck will not start. they will tell you that the exhaust needs to be cleaned. the kity get pluged up with soot and needs cleaned. when your pulling a trailer.

well just to clear it up for you i did call a local dealer and yes there is a such thing. its a diesel exhaust cleaning they do something to the back part of the exuast. so thanks you asked for help and i gave. if im lieing why dont you call your lacal dealer that has a diesel tech there, and tell them you pull a trailer, and the truck will not start. they will tell you that the exhaust needs to be cleaned. the kity get pluged up with soot and needs cleaned. when your pulling a trailer.

Actually its called a DPF, like stated above, that is what they clean...not after 5k miles though, many miles down the road from now...many many! It will go into regeneration and "clean" itself after a shorter period...after a LONG time, you may need to replace/clean the DPF ...

Please just do a search and find all of your answers, its all here!!!!!!

As for the origional poster...some guys do see increase in mileage by deleting the DPF, some dont...I would suggest tuning it via EFI live, have it sent out, your ECM that is, to on of the vendors on here and they will tune it or do it yourself if comfortable...I still think a canned tune will do it...

I Have An 07.5 And If I Baby It I Get 14-15. My Dealer Told Me It Is Get 1 Mpg Better But I Think He Is Full Of Crap. He Also Told Me My Tires Were Pulling My Mpg's Down. I Have 285's On The Truck And It Never Bothered My 03. Also Tried A Bully Dog Pmt On The Truck To Get Mpg's. For Anyone Looking At One Of Those Stay Away For It On An Lmm.

My 7.5 gets better mileage as miles get on it.. with my mods - tires/programer... get 17-18 mixed .. got 23 at 70mph over the weekend for 120 miles going to the beach... regen is every 400 miles or so if not towing. If you lead foot it.. you wont get it...

Before tires, programmer... 70mph was around 20 mpg and 15-16 mixed...

All the figures are "without" a regen factored in...

Completely stock 2008 LMM:
20.4mpg driving country roads, 60 - 60 mph (45 miles one way to work each day)
10.4mpg towing 12,000#'s, 70 - 75 mph (On the big road)
9.5mpg towing 12,000#'s, 90 mph (On the big road)
14,000 miles.. The most imporvement came after towing a heavy load for 3,000 miles, just as the odometer hit 10K

I Have An 07.5 And If I Baby It I Get 14-15. My Dealer Told Me It Is Get 1 Mpg Better But I Think He Is Full Of Crap. He Also Told Me My Tires Were Pulling My Mpg's Down. I Have 285's On The Truck And It Never Bothered My 03. Also Tried A Bully Dog Pmt On The Truck To Get Mpg's. For Anyone Looking At One Of Those Stay Away For It On An Lmm.
Did you adjust for the oversized tires?